1. Technical Field
The present invention relates to a method for producing an L-amino acid using a microorganism, especially L-lysine, L-threonine, L-phenylalanine, and L-tryptophan. These are industrially useful L-amino acids, for example, L-lysine, L-threonine, and L-tryptophan are useful as additives in animal feed, ingredients in health food, for amino acid infusions, and so forth. L-phenylalanine is useful as a precursor of sweeteners, and so forth.
2. Background Art
L-amino acids are industrially produced by fermentation using a microorganism belonging to the genus Brevibacterium, Corynebacterium, Escherichia, or the like. In such production methods, strains isolated from nature or artificial variants of such strains are used, and further, microorganisms modified by recombinant DNA techniques so that the activity of basic L-amino acid biosynthetic enzymes are increased are used, and so forth (EP 0643135 B, EP 0733712 B, EP 1477565 A, EP 0796912 A, EP 0837134 A, WO 01/53459, EP 1170376 A, WO 2005/010175, WO 96/17930, and U.S. Pat. No. 5,763,230).
When a culture of bacteria is performed for the purpose of producing a substance, excessive proliferation of the microorganisms generally decreases distribution of substrates to the objective products, and therefore it may be necessary to restrict the addition of required nutrients in medium. Examples of the nutrients which may need to be restricted include the required amino acids and phosphorus. A method is described in EP 0643135 B, wherein excessive proliferation of bacteria is suppressed by maintaining the phosphorus concentration in the culture medium to a certain range.